Solar + EV in Temecula: The Real Total Cost When You Charge Your Car on Sunshine

Adrian Marin|Independent Solar Advisor, Temecula CA

Helping Riverside County homeowners navigate SCE rates and solar options since 2020

Temecula homeowners buying an electric vehicle and solar in the same year are sitting on a combination that most installers never fully model for them. The federal incentives alone stack to $30,000 or more when you run both credits through in a single tax year. The 10-year transportation and energy cost comparison versus gas car plus grid power shows savings of $40,000 to $60,000 for a typical I-15 commuter household. But the math only works if you size the solar system correctly from the start, time your EV charging around SCE rate windows, and understand how NEM 3.0 changes the self-consumption equation. This guide covers everything a Temecula homeowner needs to know before signing a contract for either the solar or the vehicle.

How an EV Rewrites Your Solar Sizing Calculation

The standard solar sizing approach looks at your last 12 months of SCE bills and sizes a system to cover 90 to 100 percent of your historical usage. That works well for a household with stable electricity consumption. Add an EV and the model breaks down immediately, because your future consumption is materially different from your past consumption.

The numbers are straightforward. The average EV in California is driven roughly 12,000 miles per year. At an efficiency rate of 3.5 miles per kilowatt-hour (a reasonable average for vehicles like the Tesla Model Y, Chevy Bolt, or Ford Mustang Mach-E), 12,000 miles requires approximately 3,400 kWh of electricity annually. Push that to 15,000 miles per year for a commuter driving 40 to 50 miles daily on the I-15 to San Diego or up to Riverside, and you are looking at 4,300 kWh per year.

A typical Temecula home without an EV uses 10,000 to 14,000 kWh per year. Add an EV and total demand rises to 13,000 to 19,000 kWh. At Temecula's solar resource of 5.5 peak sun hours per day, covering that additional EV load requires an additional 2.0 to 2.5 kW of solar capacity beyond what you would otherwise install for the house alone. If the original design called for an 8 kW system, the EV-adjusted design should be 10 to 10.5 kW.

The reason this matters is that undersizing at installation is expensive to fix later. Adding panels after the fact requires a new permit, may require a new inverter if the existing unit is already at capacity, and resets the utility interconnection process. Every solar company operating in Temecula will tell you it is far less costly to oversize by one or two panels at initial installation than to come back 18 months later for an adder project. If you know an EV is coming within three years, size for it now.

The True Cost Comparison: Grid Charging vs. Solar Charging

To understand why charging from solar is worth the system investment, you need to run the actual per-mile fuel cost comparison under Temecula-specific conditions.

Gas at Temecula and Murrieta stations has averaged $4.50 to $5.00 per gallon through 2024 and 2025, running higher than the California average because of the Inland Empire's position at the end of the distribution chain. A gas vehicle getting 28 miles per gallon pays $0.16 to $0.18 per mile in fuel. On 12,000 miles per year, that is $1,920 to $2,160 in annual gas cost.

An EV charging entirely from the SCE grid on the ITEV-1 off-peak rate (approximately $0.13 to $0.16 per kWh) costs about $0.04 to $0.05 per mile. On 12,000 miles, that is $480 to $600 per year -- a meaningful improvement over gas. But using the Tesla Supercharger on Ynez Road instead of home charging changes the picture: Supercharger rates in Southern California run $0.35 to $0.50 per kWh, pushing per-mile cost to $0.10 to $0.14, which erodes most of the fuel cost advantage.

An EV charging from a home solar system shifts the economics again. The relevant cost for solar-charged miles is not the retail rate you would otherwise pay -- it is the avoided cost of grid electricity. For a Temecula homeowner on a TOU-D plan, daytime rates run $0.28 to $0.35 per kWh during off-peak hours and $0.40 to $0.55 per kWh during the on-peak window (4pm to 9pm). Charging during solar production hours avoids those retail rates entirely. At a blended avoided rate of $0.32 per kWh and an EV efficiency of 3.5 miles per kWh, the per-mile cost drops to about $0.09 -- and if the solar system is already paid off or nearly paid off, that cost trends toward zero on the marginal electricity basis.

The full picture over a 10-year horizon is in the comparison table below.

10-Year Household Cost Comparison: Gas Car + Grid vs. EV + Solar

The table below models a Temecula household driving 12,000 miles per year. Solar scenario assumes a 10 kW system installed in Year 1 covering both home and EV load, financed at 6.99% over 20 years. Gas price inflation assumed at 3% per year. SCE rate inflation assumed at 4% per year (consistent with SCE's 10-year historical average). Federal incentives applied in Year 1.

Estimates reflect Temecula market conditions as of 2025. Gas price baseline: $4.75/gal. SCE baseline: $0.28/kWh blended TOU-D. Solar system: 10 kW installed at $3.90/W gross, $2.73/W after 30% ITC. EV credit assumes qualifying vehicle and sufficient federal tax liability. Individual results vary. Consult a tax professional before claiming credits.

Smart Charging Under NEM 3.0: Timing Your EV to Maximize Self-Consumption

NEM 3.0 changed the economics of solar exports dramatically. Under the old NEM 2.0 rules, excess solar sent to the grid earned near-retail credits that you could use at night. Under NEM 3.0, export rates average $0.04 to $0.08 per kWh -- a fraction of the $0.28 to $0.55 per kWh you pay to buy electricity back during peak hours. The financial implication is clear: every kilowatt-hour you self-consume is worth 4 to 7 times more than every kilowatt-hour you export.

Your EV is the single largest load you can control in real time. Charging the car during peak solar production hours -- roughly 9am to 3pm -- means the energy going into the battery came directly from your panels rather than flowing to the grid at $0.06 and then being replaced by grid power at $0.35. A 40 kWh EV battery that needs a full charge each weekday represents a potential load of 11.4 kW per charging session (on a Level 2 charger at 48 amps). That load, timed to solar production, can absorb the majority of a 10 kW system's midday output directly rather than exporting it.

The SCE on-peak window under TOU-D and ITEV-1 plans runs from 4pm to 9pm on weekdays. This is the window you absolutely want to avoid charging during. A full charge at peak rates (approximately $0.48/kWh) costs nearly four times more than charging during the off-peak window ($0.13/kWh). If you cannot charge during solar production hours, the next best option is overnight between 11pm and 6am, when ITEV-1 off-peak rates apply.

Most modern EVs and Level 2 chargers allow scheduled charging. Tesla, Ford, and GM all offer scheduled departure features through their mobile apps that let you set a target departure time and charge window. Program the charger to run from 9am to 2pm if you leave the car home during work hours, or from 11pm to 5am if the car needs to charge overnight. Avoid the 4pm to 9pm window every day -- the rate difference alone is worth $400 to $600 per year on a full EV charging load.

Bidirectional Charging: V2H and V2G in Temecula

The next generation of EV value goes beyond just charging from solar. Bidirectional charging allows an EV to discharge energy back into the home (vehicle-to-home, V2H) or back into the utility grid (vehicle-to-grid, V2G). For Temecula homeowners who face SCE PSPS shutoff events during wildfire season and Santa Ana wind events, V2H capability turns the EV into a mobile battery backup.

The Ford F-150 Lightning is the most practical V2H vehicle currently available in the US market. With an 80 to 131 kWh battery pack, the Lightning can power an average Temecula home for two to five days through the Ford Intelligent Backup Power system, which requires a Ford-certified home integration kit and a licensed electrical contractor for installation. The system automatically detects a grid outage and begins discharging to the home. When the grid returns, the truck resumes normal charging.

The Nissan LEAF with a CHAdeMO port (40 kWh and 62 kWh variants) supports V2H through the Nissan Energy Sharing solution. This technology has been commercially available in Japan for several years and is approaching broader US availability through third-party bidirectional EVSE (electric vehicle supply equipment) from companies like Wallbox and Fermata Energy. If you are purchasing a LEAF specifically for V2H capability, confirm the vehicle has a CHAdeMO port -- the newer LEAF with CCS-only connection does not currently support V2H in the US.

Vehicle-to-grid (V2G) technology would allow your EV to sell energy back to SCE during peak demand periods, potentially generating revenue during the 4pm to 9pm window when SCE rates are highest. California utilities are actively piloting V2G programs. SCE's Vehicle Grid Integration (VGI) working group has outlined rate structures for V2G participants, but commercial availability for residential customers in the Temecula service territory is still in early stages. This is worth tracking if you are buying a V2G-capable vehicle now -- the infrastructure to monetize that capability is coming within the next two to three years.

Stacking Federal Incentives in One Year: Solar ITC + EV Tax Credit

The federal incentive stack available to a Temecula household buying both solar and an EV in the same tax year is one of the most underutilized opportunities in residential energy finance.

Combining the 30% solar ITC on a $39,000 system ($11,700 credit) with the $7,500 EV credit in a single tax year reduces your combined federal tax liability by $19,200. For a household with sufficient tax liability to absorb both credits -- which requires roughly $19,200 in federal income taxes owed for the year -- that is the effective cost reduction on the combined investment. Most households earning $120,000 or more in Riverside County will have sufficient liability to use both credits in Year 1.

How to Size Your Solar System When Buying Both in the Same Year

The practical sizing question is: exactly how large should the solar system be when you are installing it at the same time as buying an EV?

Start with your home's actual annual kWh usage from the last 12 SCE bills. Temecula homes typically range from 10,000 to 16,000 kWh per year depending on home size, pool, and whether you have gas or electric HVAC. Then add your projected EV charging load. Use this formula: annual miles divided by vehicle efficiency (miles per kWh) = annual EV electricity demand.

For a household using 12,000 kWh per year with a 30-mile daily commute on an EV rated at 3.5 miles per kWh:

Round up to the nearest half-kilowatt and account for a degradation buffer. Solar panels lose roughly 0.5% of production capacity per year. A system designed to cover 100% of Year 1 load will cover only about 95% in Year 10. For EV households where the production shortfall would otherwise be purchased at peak SCE rates, sizing to 105% of projected demand in Year 1 is a sound approach.

If battery storage is part of the plan, add another 10 kWh per battery unit to your solar sizing. A 10 kWh battery that charges fully every day during peak solar production and discharges fully every evening adds roughly 3,650 kWh per year of additional self-consumption demand on the solar system. Without additional panels, adding a battery can actually increase your net annual grid import if the solar system was not sized with the battery in mind.

Temecula Context: I-15 Commuters, Supercharger Access, and Local Gas Prices

The economics of solar plus EV are particularly favorable for Temecula residents for reasons specific to this market.

The I-15 corridor between Temecula and San Diego is approximately 60 miles each way, with typical commute times of 45 minutes in light traffic and 75 to 90 minutes during peak congestion. A daily commuter driving 120 miles round-trip uses roughly 34 kWh per day in a typical EV -- more than a full charge for many vehicles. That commuter needs either a Level 2 charger at home capable of restoring a full charge overnight, or access to charging infrastructure along the route.

The Tesla Supercharger on Ynez Road serves as a convenient top-up location for Temecula-based Tesla drivers, but at $0.35 to $0.50 per kWh, using it as a primary charging source costs $1,400 to $2,000 per year on the daily commute load -- significantly more than home solar charging. The smarter pattern for I-15 commuters: charge at home from solar whenever possible, use the Supercharger only for road trips or emergency situations.

Inland Empire gas prices consistently run $0.15 to $0.25 per gallon above Los Angeles coastal prices because the region sits at the end of the fuel distribution chain. During summer refinery switchover periods and after any supply disruption, Temecula and Murrieta gas prices spike first and recover last. Temecula drivers who switched from gas to solar-charged EVs in 2022 avoided the worst of the $6.00 to $6.50 per gallon spike that hit the region in June of that year.

The SCE ITEV-1 rate plan is designed specifically for EV owners and offers the most favorable charging rates for solar-plus-EV households. Under ITEV-1, a dedicated EV meter measures charging separately from home usage, enabling SCE to apply EV-specific rates to the vehicle load without affecting home rate calculations. Ask your solar installer or SCE directly about ITEV-1 enrollment before your EV arrives -- the enrollment window is most efficient when completed before you start charging.